how to print std::map with spdlog

Question

int main()
{
    std::map<std::string, std::string> o;
    o["foo"] = "foo value";
    spdlog::info(o);
    return 0;
}

Got error: static_assert failed due to requirement 'formattable' "Cannot format argument. To make type T formattable provide a formatter specialization: https://fmt.dev/latest/api.html#formatting-user-defined-types"

Have you tried following the link and implementing a formatter? — Alan Birtles, Apr 26 '20 at 06:56
I following the link , but got error : class template specialization of 'formatter' not in a namespace enclosing 'v6' — langyu, Apr 26 '20 at 07:07

score 0 · Answer 1 · answered May 07 '20 at 20:35

spdlog only support types that have operator << (with #include <fmt/ostream.h>)

You have 2 options:

Implement function: std::ostream& operator <<(std::ostream&, const std::map<std::string, std::string>&)
Log key and value in the loop:

for (const auto&[k, v] : o)
{
    spdlog::info("key is {}, value is {}", k, v);
}

1 Answers1